Cisco IOS NAT Skinny Call Control Protocol Vulnerability

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Updated:December 10, 2011
Document ID:1517405045004552

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Advisory ID: cisco-sa-20080924-sccp

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-sccp

Revision 1.1

For Public Release 2008 September 24 16:00  UTC (GMT)

Summary

A series of segmented Skinny Call Control Protocol (SCCP) messages may cause a Cisco IOS device that is configured with the Network Address Translation (NAT) SCCP Fragmentation Support feature to reload.

Cisco has released free software updates that address this vulnerability. A workaround that mitigates this vulnerability is available.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-sccp.

Note: The September 24, 2008 IOS Advisory bundled publication includes twelve Security Advisories. Eleven of the advisories address vulnerabilities in Cisco's IOS software, and one advisory addresses vulnerabilities in Cisco Unified Communications Manager. Each Advisory lists the releases that correct the vulnerability described in the Advisory.

Individual publication links are listed below:

Affected Products

Vulnerable Products

This security advisory applies to all Cisco products that run Cisco IOS Software configured for NAT and that support the NAT SCCP Fragmentation Support feature. This feature was first introduced in Cisco IOS version 12.4(6)T.

To verify if NAT is enabled on a Cisco IOS device log into the device and issue the command show ip nat statistics. The following example shows a device configured with NAT: 

Router# show ip nat statistics

Total translations: 2 (0 static, 2 dynamic; 0 extended)
Outside interfaces: Serial0
Inside interfaces: Ethernet1
Hits: 135  Misses: 5
Expired translations: 2
Dynamic mappings:
-- Inside Source
access-list 1 pool mypool refcount 2
 pool mypool: netmask 255.255.255.0
        start 192.168.10.1 end 192.168.10.254
        type generic, total addresses 14, allocated 2 (14%), misses 0

Alternatively, you can use the show running-config | include ip nat command to verify if NAT has been enabled on the router interfaces.

Note: With reference to NAT, the term "inside" refers to those networks that will be translated. Inside this domain, hosts will have addresses in one address space, while on the "outside", they will appear to have addresses in another address space when NAT is configured. The first address space is referred to as the local address space and the second is referred to as the global address space. The ip nat inside and ip nat outside interface commands must be present on the corresponding router interfaces in order for NAT to be enabled.

In order to determine the software that runs on a Cisco IOS product, log in to the device and issue the show version command to display the system banner. Cisco IOS software identifies itself as "Internetwork Operating System Software" or simply "IOS." On the next line of output, the image name displays between parentheses, followed by "Version" and the Cisco IOS release name. Other Cisco devices do not have the show version command or give different output.

The following example shows output from a device that runs an IOS image:

router>show version
Cisco IOS Software, 7200 Software (C7200-ADVSECURITYK9-M), Version 12.4(6)T2, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Tue 16-May-06 16:09 by kellythw
<more output removed for brevity>

Products Confirmed Not Vulnerable

Cisco IOS XR and IOS XE are not affected by this vulnerability.

Cisco IOS devices not explicitly configured for NAT are not vulnerable.

No other Cisco products are currently known to be affected by these vulnerabilities.

Details

The Skinny Call Control Protocol (SCCP) enables voice communication between an SCCP client and a Call Manager (CM). Typically, the CM provides service to the SCCP clients on TCP Port 2000 by default. Initially, an SCCP client connects to the CM by establishing a TCP connection; the client will also establish a TCP connection with a secondary CM, if available.

The NAT SCCP Fragmentation Support feature prevents skinny control message exchanges from failing in a TCP segmentation scenario because the NAT Skinny Application Layer Gateway (ALG) is able to reassemble the skinny control messages. A segmented payload that requires an IP or port translation will no longer be dropped. The NAT SCCP Fragmentation Support feature was introduced in Cisco IOS version 12.4(6)T.

A series of fragmented SCCP messages may cause a Cisco IOS router that is running the NAT SCCP Fragmentation Support feature to reload.

This vulnerability is documented in Cisco Bug ID CSCsg22426 ( registered customers only) and CSCsi17020 ( registered customers only) , and has been assigned CVE identifiers CVE-2008-3810 and CVE-2008-3811.

Vulnerability Scoring Details

Cisco has provided scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this Security Advisory is done in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability severity and helps determine urgency and priority of response.

Cisco has provided a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks.

Cisco has provided an FAQ to answer additional questions regarding CVSS at

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html .

Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at

http://intellishield.cisco.com/security/alertmanager/cvss .

CSCsg22426 - Cisco IOS Skinny Call Control Protocol (SCCP) Vulnerability

Calculate the environmental score of CSCsg22426

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

CSCsi17020 - Router may reload after NAT with certain skinny packets

Calculate the environmental score of CSCsi17020

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed

Impact

Successful exploitation of this vulnerability may cause the affected device to reload. Repeated exploitation will result in a denial of service (DoS) condition.

Software Versions and Fixes

When considering software upgrades, also consult http://www.cisco.com/go/psirt and any subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco Technical Assistance Center (TAC) or your contracted maintenance provider for assistance.

Each row of the Cisco IOS software table (below) names a Cisco IOS release train. If a given release train is vulnerable, then the earliest possible releases that contain the fix (along with the anticipated date of availability for each, if applicable) are listed in the "First Fixed Release" column of the table. The "Recommended Release" column indicates the releases which have fixes for all the published vulnerabilities at the time of this Advisory. A device running a release in the given train that is earlier than the release in a specific column (less than the First Fixed Release) is known to be vulnerable. Cisco recommends upgrading to a release equal to or later than the release in the "Recommended Releases" column of the table.

Major Release

     Availability of Repaired Releases

Affected 12.0-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.0 based releases

Affected 12.1-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.1 based releases

Affected 12.2-Based Releases

First Fixed Release

Recommended Release

12.2

Not Vulnerable

  

12.2B

Not Vulnerable

  

12.2BC

Not Vulnerable

  

12.2BW

Not Vulnerable

  

12.2BX

Not Vulnerable

  

12.2BY

Not Vulnerable

  

12.2BZ

Not Vulnerable

  

12.2CX

Not Vulnerable

  

12.2CY

Not Vulnerable

  

12.2CZ

Not Vulnerable

  

12.2DA

Not Vulnerable

  

12.2DD

Not Vulnerable

  

12.2DX

Not Vulnerable

  

12.2EW

Not Vulnerable

  

12.2EWA

Not Vulnerable

  

12.2EX

Not Vulnerable

  

12.2EY

Not Vulnerable

  

12.2EZ

Not Vulnerable

  

12.2FX

Not Vulnerable

  

12.2FY

Not Vulnerable

  

12.2FZ

Not Vulnerable

  

12.2IRB

Not Vulnerable

  

12.2IXA

Not Vulnerable

  

12.2IXB

Not Vulnerable

  

12.2IXC

Not Vulnerable

  

12.2IXD

Not Vulnerable

  

12.2IXE

Not Vulnerable

  

12.2IXF

Not Vulnerable

  

12.2IXG

Not Vulnerable

  

12.2JA

Not Vulnerable

  

12.2JK

Not Vulnerable

  

12.2MB

Not Vulnerable

  

12.2MC

Not Vulnerable

  

12.2S

Not Vulnerable

  

12.2SB

Not Vulnerable

  

12.2SBC

Not Vulnerable

  

12.2SCA

Not Vulnerable

  

12.2SE

Not Vulnerable

  

12.2SEA

Not Vulnerable

  

12.2SEB

Not Vulnerable

  

12.2SEC

Not Vulnerable

  

12.2SED

Not Vulnerable

  

12.2SEE

Not Vulnerable

  

12.2SEF

Not Vulnerable

  

12.2SEG

Not Vulnerable

  

12.2SG

Not Vulnerable

  

12.2SGA

Not Vulnerable

  

12.2SL

Not Vulnerable

  

12.2SM

Not Vulnerable

  

12.2SO

Not Vulnerable

  

12.2SRA

Not Vulnerable

  

12.2SRB

Not Vulnerable

  

12.2SRC

Not Vulnerable

  

12.2SU

Not Vulnerable

  

12.2SV

Not Vulnerable

  

12.2SVA

Not Vulnerable

  

12.2SVC

Not Vulnerable

  

12.2SVD

Not Vulnerable

  

12.2SW

Not Vulnerable

  

12.2SX

Not Vulnerable

  

12.2SXA

Not Vulnerable

  

12.2SXB

Not Vulnerable

  

12.2SXD

Not Vulnerable

  

12.2SXE

Not Vulnerable

  

12.2SXF

Not Vulnerable

  

12.2SXH

Not Vulnerable

  

12.2SY

Not Vulnerable

  

12.2SZ

Not Vulnerable

  

12.2T

Not Vulnerable

  

12.2TPC

Not Vulnerable

  

12.2XA

Not Vulnerable

  

12.2XB

Not Vulnerable

  

12.2XC

Not Vulnerable

  

12.2XD

Not Vulnerable

  

12.2XE

Not Vulnerable

  

12.2XF

Not Vulnerable

  

12.2XG

Not Vulnerable

  

12.2XH

Not Vulnerable

  

12.2XI

Not Vulnerable

  

12.2XJ

Not Vulnerable

  

12.2XK

Not Vulnerable

  

12.2XL

Not Vulnerable

  

12.2XM

Not Vulnerable

  

12.2XN

Not Vulnerable

  

12.2XNA

Not Vulnerable

  

12.2XNB

Not Vulnerable

  

12.2XO

Not Vulnerable

  

12.2XQ

Not Vulnerable

  

12.2XR

Not Vulnerable

  

12.2XS

Not Vulnerable

  

12.2XT

Not Vulnerable

  

12.2XU

Not Vulnerable

  

12.2XV

Not Vulnerable

  

12.2XW

Not Vulnerable

  

12.2YA

Not Vulnerable

  

12.2YB

Not Vulnerable

  

12.2YC

Not Vulnerable

  

12.2YD

Not Vulnerable

  

12.2YE

Not Vulnerable

  

12.2YF

Not Vulnerable

  

12.2YG

Not Vulnerable

  

12.2YH

Not Vulnerable

  

12.2YJ

Not Vulnerable

  

12.2YK

Not Vulnerable

  

12.2YL

Not Vulnerable

  

12.2YM

Not Vulnerable

  

12.2YN

Not Vulnerable

  

12.2YO

Not Vulnerable

  

12.2YP

Not Vulnerable

  

12.2YQ

Not Vulnerable

  

12.2YR

Not Vulnerable

  

12.2YS

Not Vulnerable

  

12.2YT

Not Vulnerable

  

12.2YU

Not Vulnerable

  

12.2YV

Not Vulnerable

  

12.2YW

Not Vulnerable

  

12.2YX

Not Vulnerable

  

12.2YY

Not Vulnerable

  

12.2YZ

Not Vulnerable

  

12.2ZA

Not Vulnerable

  

12.2ZB

Not Vulnerable

  

12.2ZC

Not Vulnerable

  

12.2ZD

Not Vulnerable

  

12.2ZE

Not Vulnerable

  

12.2ZF

Not Vulnerable

  

12.2ZG

Not Vulnerable

  

12.2ZH

Not Vulnerable

  

12.2ZJ

Not Vulnerable

  

12.2ZL

Not Vulnerable

  

12.2ZP

Not Vulnerable

  

12.2ZU

Not Vulnerable

  

12.2ZX

Not Vulnerable

  

12.2ZY

Not Vulnerable

  

12.2ZYA

Not Vulnerable

  

Affected 12.3-Based Releases

First Fixed Release

Recommended Release

There are no affected 12.3 based releases

Affected 12.4-Based Releases

First Fixed Release

Recommended Release

12.4

Not Vulnerable

  

12.4JA

Not Vulnerable

  

12.4JK

Not Vulnerable

  

12.4JL

Not Vulnerable

  

12.4JMA

Not Vulnerable

  

12.4JMB

Not Vulnerable

  

12.4JMC

Not Vulnerable

  

12.4JX

Not Vulnerable

  

12.4MD

12.4(11)MD4

12.4(15)MD1

12.4MR

12.4(16)MR

12.4(19)MR

12.4SW

12.4(15)SW2; Available on 28-SEP-08

12.4(15)SW2; Available on 28-SEP-08

12.4T

12.4(11)T4

12.4(15)T2

12.4(20)T

12.4(6)T11

12.4(9)T5

12.4(15)T7

12.4XA

Not Vulnerable

  

12.4XB

Not Vulnerable

  

12.4XC

Vulnerable; first fixed in 12.4T

12.4(15)T7

12.4XD

Not Vulnerable

  

12.4XE

Vulnerable; first fixed in 12.4T

12.4(15)T7

12.4XF

Vulnerable; first fixed in 12.4T

12.4(15)T7

12.4XG

12.4(9)XG3

12.4(9)XG3

12.4XJ

Vulnerable; first fixed in 12.4T

12.4(15)T7

12.4XK

Vulnerable; first fixed in 12.4T

12.4(15)T7

12.4XL

12.4(15)XL2

12.4(15)XL2

12.4XM

12.4(15)XM1

12.4(15)XM1

12.4XN

Vulnerable; contact TAC

  

12.4XP

Vulnerable; contact TAC

  

12.4XQ

Not Vulnerable

  

12.4XR

Not Vulnerable

  

12.4XT

Vulnerable; first fixed in 12.4T

12.4(15)T7

12.4XV

Vulnerable; contact TAC

  

12.4XW

12.4(11)XW7

12.4(11)XW9

12.4XY

Not Vulnerable

  

12.4XZ

Not Vulnerable

  

12.4YA

Not Vulnerable

  

Workarounds

As workaround, an administrator can disable SCCP NAT support using the no ip nat service skinny tcp port 2000 command, as shown in the following example:

Router(config)# no ip nat service skinny tcp port 2000

Note: If your Cisco CallManager is using a TCP port for skinny signaling different from the default port (2000), you need to adjust this command accordingly.

Obtaining Fixed Software

Cisco has released free software updates that address these vulnerabilities. Prior to deploying software, customers should consult their maintenance provider or check the software for feature set compatibility and known issues specific to their environment.

Customers may only install and expect support for the feature sets they have purchased. By installing, downloading, accessing or otherwise using such software upgrades, customers agree to be bound by the terms of Cisco's software license terms found at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html, or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Do not contact psirt@cisco.com or security-alert@cisco.com for software upgrades.

Customers with Service Contracts

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained through the Software Center on Cisco's worldwide website at http://www.cisco.com.

Customers using Third Party Support Organizations

Customers whose Cisco products are provided or maintained through prior or existing agreements with third-party support organizations, such as Cisco Partners, authorized resellers, or service providers should contact that support organization for guidance and assistance with the appropriate course of action in regards to this advisory.

The effectiveness of any workaround or fix is dependent on specific customer situations, such as product mix, network topology, traffic behavior, and organizational mission. Due to the variety of affected products and releases, customers should consult with their service provider or support organization to ensure any applied workaround or fix is the most appropriate for use in the intended network before it is deployed.

Customers without Service Contracts

Customers who purchase direct from Cisco but do not hold a Cisco service contract, and customers who purchase through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should acquire upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC contacts are as follows.

  • +1 800 553 2447 (toll free from within North America)
  • +1 408 526 7209 (toll call from anywhere in the world)
  • e-mail: tac@cisco.com

Customers should have their product serial number available and be prepared to give the URL of this notice as evidence of entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC.

Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for additional TAC contact information, including localized telephone numbers, and instructions and e-mail addresses for use in various languages.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.

Status of this Notice: Final

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.

A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.


Distribution

This advisory is posted on Cisco's worldwide website at:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20080924-sccp

In addition to worldwide web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients.

  • cust-security-announce@cisco.com
  • first-teams@first.org
  • bugtraq@securityfocus.com
  • vulnwatch@vulnwatch.org
  • cisco@spot.colorado.edu
  • cisco-nsp@puck.nether.net
  • full-disclosure@lists.grok.org.uk
  • comp.dcom.sys.cisco@newsgate.cisco.com

Future updates of this advisory, if any, will be placed on Cisco's worldwide website, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the above URL for any updates.


Revision History

Revision 1.1

2009-April-16

Removed references to the combined software table, as it is now outdated

Revision 1.0

2008-September-24

Initial public release

Cisco Security Procedures

Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's worldwide website at http://www.cisco.com/web/about/security/psirt/security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt.